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J C Jansen

Publications and source records attributed to J C Jansen.

17 recordsLinked to original sources
PubMed2001

One-step synthesis of a highly active, mesoporous, titanium-containing silica by using bifunctional templating.

A highly active, three-dimensional, mesoporous titanosilica, TiTUD-1, with comparable properties to Ti-grafted mesoporous silica MCM-41, has been prepared in a one-step synthesis. A non-surfactant chemical, triethanolamine, was used as a template molecule. Triethanolamine easily forms complexes with titanium alkoxides, yielding titanatrane complexes, which together with free triethanolamine form meso-sized aggregates that template mesopores upon increasing the temperature of the synthesis mixture. Triethanolamine served as both mesopore template and ligand for the titanium complexes, which represent the majority of the catalytic-site precursors. The formation of the silica network and the titanium insertion were followed by a combination of diffuse reflectance UV/ Vis/NIR and FTIR spectroscopy. A titanium-rich phase was obtained on the mesopore surfaces during calcination, allowing for easy accessibility of the reactants to the catalytic sites. TiTUD-1 is about six times more active than framework-substituted Ti-MCM-41 and has similar activity to Ti-grafted MCM-41.

Journal Article↗
PubMed2001

Nearly all hereditary paragangliomas in the Netherlands are caused by two founder mutations in the SDHD gene.

Hereditary paragangliomas or glomus tumors are usually benign slow-growing tumors in the head and neck region. The inheritance pattern of hereditary paraganglioma is autosomal dominant with imprinting. Recently, we have identified the SDHD gene encoding subunit D of the mitochondrial respiratory chain complex II as one of the genes involved in hereditary paragangliomas. Here, we demonstrate that two founder mutations, Asp92Tyr and Leu139Pro, are responsible for paragangliomas in 24 and 6 of the 32 independently ascertained Dutch paraganglioma families, respectively. These two mutations were also detected among 20 of 55 isolated patients. Ten of the isolated patients had multiple paragangliomas, and in eight of these SDHD germline mutations were found, indicating that multicentricity is a strong predictive factor for the hereditary nature of the disorder in isolated patients. In addition, we demonstrate that the maternally derived wild-type SDHD allele is lost in tumors from mutation-carrying patients, indicating that SDHD functions as a tumor suppressor gene.

DNA Mutational Analysis↗
PubMed2001

Management of carotid body tumors.

The carotid body tumor is a rare neoplasm that has generated much literature over the past century, and for which continued controversy exists regarding natural history, biologic behavior, proper technique of excision, and the risk of morbidity and mortality. This article discusses overall management of carotid body tumors.

Aged↗
PubMed2001

Evaluation of nitrification-inhibition measurements.

A screening method for nitrification-inhibition determination has been evaluated at two laboratories, one in Sweden and one in Spain. Allyl-thiourea (ATU), methanol, chromium and zinc were used as reference toxicants in combination with different kinds of full-scale sludge and sludge produced in the laboratory. Different results were obtained with different combinations of activated sludge and toxicants. It was found that activated sludge often exposed to small amounts of a variety of toxic substances may build up a general resistance to toxic substances. Specific adaptation to certain substances was also observed. Domestic activated sludge responded in the same way to ATU regardless of whether it originated from Sweden or Spain. Synthetic sludge and domestic sludge exhibited the same inhibition of nitrification when tested with ATU as a toxicant. Synthetic activated sludge from two laboratory-scale plants run in parallel did not exhibit exactly the same sensitivity to certain toxicants. The variation in repeated tests with the synthetic sludges was about the same as for repeated tests with full-scale sludge and for other biological toxicity tests. Limits of detection were calculated to be about 5% for a single sample with three blanks as references at both the laboratories.

Chromium↗
PubMed2000

Estimation of growth rate in patients with head and neck paragangliomas influences the treatment proposal.

BACKGROUND: Extraadrenal paragangliomas of the head and neck are tumors with variable clinical behavior. Because tumor growth as well as surgery can cause disabling loss of function, knowledge of the natural history of paragangliomas is important for the development of treatment strategies. METHODS: The tumor volume, growth rate, and tumor doubling time of 48 paragangliomas at different anatomic locations in the head and neck region were estimated retrospectively using sequential radiologic imaging. RESULTS: During a mean follow-up period of 4.2 years, a volume increase of > 20% was observed in 60% of the paragangliomas. In these cases the median growth rate was 1.0 mm/year and the median tumor doubling time was 4. 2 years. More growing tumors were observed in intermediate size tumors than in very small or large paragangliomas, suggesting a biphasic growth pattern. CONCLUSIONS: The majority of head and neck paragangliomas have a very low growth rate. Although management of paragangliomas also is determined by other parameters, preoperative estimation of the tumor doubling time may influence the treatment proposal. A "wait and scan" policy must be considered in all cases.

Adult↗
PubMed1998

Founder effect at PGL1 in hereditary head and neck paraganglioma families from the Netherlands.

PGL1, a gene responsible for hereditary paragangliomas of the head and neck, recently was mapped to a 2-cM interval on chromosome 11q22-q23, by linkage and haplotype-sharing analysis of a large multibranch Dutch family. We determined the disease-linked haplotype, as defined by 13 markers encompassing a large interval on 11q21-q23, in 10 additional families ascertained from the same geographical locale. Alleles were identical for six contiguous markers, spanning a genetic distance of 6 cM and containing PGL1. Despite this strong indication of a common ancestor, no kinships between the families could be demonstrated through genealogical surveys going back to 1800 a.d. We conclude that a single ancestral mutation is responsible for most, if not all, hereditary paragangliomas, in this region of The Netherlands, and that strong founder effects may exist at the PGL1 locus.

Chromosome Mapping↗
PubMed1996

First experiences with genetic counselling based on predictive DNA diagnosis in hereditary glomus tumours (paragangliomas).

Hereditary glomus tumour (MIM 168,000) or paraganglioma (PGL) is a slowly progressive disorder causing benign tumour growth predominantly in the head and neck region. Though benign in nature the tumours can lead to severe morbidity. Inheritance of PGL is autosomal dominant and is strongly modified by genomic imprinting; only a paternally transmitted PGL gene leads to symptoms. A gene for PGL has recently been mapped to 11q22.3-q23. Genetic counselling on the basis of DNA linkage diagnosis was offered in an extended Dutch pedigree. Thirty-two subjects opted for further counselling, of whom 20 applied for DNA testing and participated in a standardised protocol. Sixteen cases had presymptomatic testing (paternal allele); four of these appeared to have the at risk haplotype and in two of them a glomus tumour was subsequently detected on MRI. In one case linkage results were inconclusive (recombination) and one person did not want to learn his test result. Four cases had testing for carrier status (maternal allele) of which one appeared to be a carrier. Our data show that genetic counselling gains significant accuracy when based on parent of origin, sex of the counsellee, and DNA linkage diagnosis. Moreover, a normal DNA result may prevent unnecessary worry and investigations, while an established presymptomatic diagnosis will guide adequate clinical management. The psychological impact of counselling and predictive DNA testing is unclear as yet. Further investigations into the natural history of PGL in gene carriers and into the psychological impact of DNA testing is desirable.

DNA, Neoplasm↗
PubMed1996

Confinement of PGL, an imprinted gene causing hereditary paragangliomas, to a 2-cM interval on 11q22-q23 and exclusion of DRD2 and NCAM as candidate genes.

Paragangliomas of the head and neck region, also known as glomus tumours, are mostly benign tumours of neuro-ectodermal origin. We mapped the familial form by linkage analysis in 6 families to chromosome region 11q22-q23, between the markers STMY and CD3D which currently span a 16-cM interval. Here, we performed detailed haplotype analysis of this region in a single Dutch multibranch 7-generation family. A region of 2 cM between the markers D11S938/D11S4122 and D11S1885 was shared between all patients of whom disease haplotypes could be reconstructed. In support of this localization, a recombination observed in a small French family with 2 affected nieces places the PGL gene proximal to marker D11S908, genetically coincident with D11S1885.

Chromosome Mapping↗
PubMed1992

Blood flow velocities in the vertebrobasilar system during migraine attacks--a transcranial Doppler study.

In this study, blood flow velocity in the basilar artery and both vertebral and middle cerebral arteries was measured with a transcranial Doppler device in 23 migraineurs during and outside a migraine attack. The aim of the study was to compare blood flow velocities during and outside an attack and to examine vascular reactivity to voluntary hyperventilation during both conditions. No differences in blood flow velocity were found. Although blood pressure was increased and end-expiratory CO2 decreased during the attack, this exerted no influence on blood flow velocity. Neither was a difference in vascular reactivity to voluntary hyperventilation detected between the two conditions. These findings support the notion of functional integrity of the examined large arteries during migraine attacks without aura.

Adult↗
PubMed1991

Blood flow velocity changes in migraine attacks--a transcranial Doppler study.

A pulsed Doppler device was used to measure blood flow velocities in the common carotid artery, the extracranial part of the internal carotid artery, the external carotid artery, the middle cerebral artery, and the anterior cerebral artery in 31 migraineurs without aura (n = 27) and with aura (n = 4), both during and outside an attack. The aims were to compare blood flow velocity during and between migraine attacks and to study asymmetries of the blood flow velocity. Compared with blood flow velocity values obtained in the attack-free interval, blood flow velocity was lower during attacks without aura in both common carotid arteries, but not in the other extra- and intracranial vessels which were examined. However, during attacks of migraine with aura, blood flow velocity tended to be lower in all examined vessels. There were no asymmetries of the blood flow velocity. We suggest that during migraine attacks without aura there is a dissociation in blood flow regulation in the common carotid and middle cerebral arteries.

Adolescent↗
PubMed1980

A scalogram analysis of behavioral strategies in severely and profoundly retarded adults.

The present study was designed to provide empirical evidence for an assumed order sequence of five behavioral strategies in 75 severely and profoundly retarded adults. A behavioral strategy was defined as a set of task-related behaviors each of which is controlled by the same stimulus properties of the materials. Four sets of tasks were used to measure four of the five strategies. Multiple presentation modes were employed to enhance the Ss' understanding of the demand characteristics of the tasks. A scalogram analysis revealed that the four sets of items met the requirements for a cumulative scale. Additional analyses were performed to identify individual items measuring a specific behavioral strategy. The obtained results indicated that most items measured one strategy although not always the one for which they were designed. The additional value of the described classification system over other, more traditional measures, is discussed.

Adolescent↗
PubMed1980

[Not Available].

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History, Ancient↗
PubMedDate not supplied

Color Doppler imaging of paragangliomas in the neck.

PURPOSE: In this study, we describe the color Doppler imaging findings in carotid body tumors and vagal body tumors. METHODS: B-mode and color Doppler imaging were performed on 17 patients who had a total of 25 previously diagnosed paragangliomas (14 carotid body tumors and 11 vagal body tumors). RESULTS: Nineteen of 25 tumors were depicted. Five small vagal body tumors in the region of the nodose ganglion and 1 carotid body tumor could not be depicted. With B-mode imaging, paragangliomas appeared as well-defined, solid, hypoechoic masses. With color Doppler imaging, hypervascularity with a low-resistance flow pattern was demonstrated in all but 1 of the 19 tumors. CONCLUSIONS: The use of color Doppler imaging in the workup of an ambiguous neck mass is advocated.

Adult↗